Cisco ASR 900 Series User Manual

meet the challenges of explosive growth in network utilization while providing the opportunity to differentiate
services without sacrificing the existing network infrastructure. The MPLS architecture is flexible and can be
employed in any combination of Layer 2 technologies. MPLS support is offered for all Layer 3 protocols,
and scaling is possible well beyond that typically offered in today’s networks.
MPLS efficiently enables the delivery of IP services over an ATM switched network. MPLS supports the
creation of different routes between a source and a destination on a purely router-based Internet backbone.
By incorporating MPLS into their network architecture, service providers can save money, increase revenue
and productivity, provide differentiated services, and gain competitive advantages.
Functional Description of MPLS
Label switching is a high-performance packet forwarding technology that integrates the performance and
traffic management capabilities of data link layer (Layer 2) switching with the scalability, flexibility, and
performance of network layer (Layer 3) routing.
Label Switching Functions
In conventional Layer 3 forwarding mechanisms, as a packet traverses the network, each router extracts all
the information relevant to forwarding the packet from the Layer 3 header. This information is then used as
an index for a routing table lookup to determine the next hop for the packet.
In the most common case, the only relevant field in the header is the destination address field, but in some
cases, other header fields might also be relevant. As a result, the header analysis must be done independently
at each router through which the packet passes. In addition, a complicated table lookup must also be done at
each router.
In label switching, the analysis of the Layer 3 header is done only once. The Layer 3 header is then mapped
into a fixed length, unstructured value called a label .
Many different headers can map to the same label, as long as those headers always result in the same choice
of next hop. In effect, a label represents a forwarding equivalence class --that is, a set of packets which,
however different they may be, are indistinguishable by the forwarding function.
The initial choice of a label need not be based exclusively on the contents of the Layer 3 packet header; for
example, forwarding decisions at subsequent hops can also be based on routing policy.
Once a label is assigned, a short label header is added at the front of the Layer 3 packet. This header is carried
across the network as part of the packet. At subsequent hops through each MPLS router in the network, labels
are swapped and forwarding decisions are made by means of MPLS forwarding table lookup for the label
carried in the packet header. Hence, the packet header does not need to be reevaluated during packet transit
through the network. Because the label is of fixed length and unstructured, the MPLS forwarding table lookup
process is both straightforward and fast.
Distribution of Label Bindings
Each> label switching router (LSR) in the network makes an independent, local decision as to which label
value to use to represent a forwarding equivalence class. This association is known as a label binding. Each
LSR informs its neighbors of the label bindings it has made. This awareness of label bindings by neighboring
routers is facilitated by the following protocols:
MPLS Basic Configuration Guide, Cisco IOS XE Everest 16.5.1 (Cisco ASR 900 Series)
2
Multiprotocol Label Switching (MPLS) on Cisco Routers
Functional Description of MPLS

Cisco ASR 900 Series Specifications

General

Product Family	ASR 900 Series
Category	Network Router
Connectivity Technology	Wired
Switching Capacity	Varies by model
Memory	Varies by model
Operating System	Cisco IOS XE
Dimensions	Varies by model
Weight	Varies by model
Form Factor	Modular
Supported Interfaces	Ethernet, Gigabit Ethernet, 10 Gigabit Ethernet, T1/E1, T3/E3, OC-3/STM-1, OC-12/STM-4, OC-48/STM-16
Ports	Varies by model
Data Link Protocol	Ethernet, Fast Ethernet, Gigabit Ethernet
Network / Transport Protocol	TCP/IP, UDP
Routing Protocol	BGP, OSPF, IS-IS, RIP, EIGRP, MPLS
Remote Management Protocol	SNMP, CLI, SSH
Features	MPLS, QoS, IPv6, NetFlow, ACLs, VRF
Power Supply	AC or DC
Operating Temperature	0 to 40°C
Storage Temperature	-40 to 70°C (-40 to 158°F)
Humidity	5% to 95% (non-condensing)

Summary

Multiprotocol Label Switching (MPLS) on Cisco Routers

Finding Feature Information

Locates information about features, caveats, and release notes.

Information About MPLS

Provides an overview of MPLS functionality and its role in networks.

How to Configure MPLS

Explains basic configuration for MPLS switching and forwarding.

Additional References

Lists related documents for Cisco IOS commands and MPLS commands.

Feature Information for MPLS on Cisco Routers

Details software release information for MPLS features.

Glossary

Defines key terms and acronyms used in the document.

MPLS Transport Profile

Restrictions for MPLS-TP on the Cisco ASR 900 Series Routers

Lists limitations and unsupported features for MPLS-TP on specific routers.

Information About MPLS-TP

Explains how MPLS Transport Profile works, including LSPs and pseudowires.

How to Configure MPLS Transport Profile

Provides steps for configuring MPLS Transport Profile, including label ranges.

Configuration Examples for MPLS Transport Profile

Offers practical examples of MPLS Transport Profile configuration scenarios.

MPLS Multilink PPP Support

Prerequisites for MPLS Multilink PPP Support

Lists requirements for enabling MPLS Multilink PPP support.

Restrictions for MPLS Multilink PPP Support

Details limitations on multilink bundles and members per bundle.

Information About MPLS Multilink PPP Support

Describes Layer 3 VPN features and QoS features supported for Multilink PPP.

How to Configure MPLS Multilink PPP Support

Guides through configuring MPLS Multilink PPP support, including bundle creation.

Configuration Examples for MPLS Multilink PPP Support

Provides sample configurations for MPLS Multilink PPP in various network scenarios.

MPLS LSP Ping, Traceroute, and AToM VCCV

Prerequisites for MPLS LSP Ping, Traceroute, and AToM VCCV

Lists prerequisites before using MPLS LSP Ping, Traceroute, and AToM VCCV features.

Restrictions for MPLS LSP Ping, Traceroute, and AToM VCCV

Details limitations on using MPLS LSP Ping and Traceroute for specific applications like AToM and VPNs.

Information About MPLS LSP Ping, Traceroute, and AToM VCCV

Explains MPLS LSP Ping operation, echo request/reply paths, and packet handling.

Command Options for ping mpls and trace mpls

Describes command options and arguments for MPLS LSP Ping and Traceroute.

Selection of FECs for Validation

Explains how to select Forwarding Equivalence Classes (FECs) for LSP validation.

Reply Mode Options for MPLS LSP Ping and Traceroute

Controls how the responding device replies to MPLS echo requests.

Packet Handling Along Return Path with an IP MPLS Router Alert

Describes how IP and MPLS packets with router alert options are handled.

Other MPLS LSP Ping and Traceroute Command Options

Details additional command options for MPLS LSP Ping and Traceroute.

MPLS LSP Ping and Traceroute Returns a Q

Troubleshoots issues when MPLS echo replies return a 'Q' code, indicating packet transmission failure.

Load Balancing for IPv4 LDP LSPs

Explains how MPLS uses source/destination addresses for load balancing.

NSR LDP Support

Finding Feature Information

Locates information about features, caveats, and release notes for NSR LDP Support.

Prerequisites for NSR LDP Support

Lists requirements for NSR LDP Support to function correctly.

Information About NSR LDP Support

Details the roles of standby RP and LDP, and NSR operation states.

How to Configure NSR LDP Support

Provides steps to enable and configure NSR LDP Support.

Configuration Examples for NSR LDP Support

Shows sample configurations for NSR LDP Support, including verification steps.

Additional References for NSR LDP Support

Lists related documents and technical assistance resources for NSR LDP Support.

Feature Information for NSR LDP Support

Provides release-specific information for NSR LDP Support features.

VPLS Configuration over MPLS-TP

VPLS over MPLS-TP

Provides an overview of VPLS implementation over MPLS-TP.

Configuring VPLS over MPLS-TP

Guides through the configuration steps for VPLS over MPLS-TP.

Verifying the Configuration

Details commands for verifying VPLS configuration and debugging.

Configuration Examples

Offers practical examples for configuring VPLS over MPLS-TP.

Feature Information for VPLS Configuration over MPLS-TP

Lists software release information for VPLS over MPLS-TP features.

Circuit Emulation Service over UDP

Finding Feature Information

Locates information about features, caveats, and release notes for Circuit Emulation over UDP.

Restrictions for Circuit Emulation Service over UDP

Lists limitations and unsupported features for Circuit Emulation Service over UDP.

Information About Circuit Emulation Service over UDP

Explains CES overview, pseudowire emulation, and CESoPSN mode.

How to Configure Circuit Emulation Service over UDP

Guides through configuring Circuit Emulation Service over UDP.

Structure-Agnostic TDM over Packet over UDP

Details the Structure-Agnostic TDM over Packet (SAToP) encapsulation method.

How to Configure Structure-Agnostic TDM over Packet

Guides through configuring Structure-Agnostic TDM over Packet (SAToP).

Example Verifying the Configuration of Structure-Agnostic TDM over Packet

Demonstrates how to verify the SAToP configuration.

Flex LSP Overview

Signaling Methods and Object Association for Flex LSPs

Explains association signaling methods for bidirectional LSPs in Flex LSP.

Associated Bidirectional Non Co-routed and Co-routed LSPs

Overviews associated bidirectional LSPs, covering non co-routed and co-routed types.

Restrictions for Flex LSP

Lists limitations and recommendations for Flex LSP deployments.

How to Configure Co-routed Flex LSPs

Guides through configuring co-routed bidirectional Flex LSPs, including setup steps.

How to Configure Non Co-routed Inter-area Flex LSP Tunnels

Details configuration steps for non co-routed inter-area Flex LSP tunnels.

Flex LSP Phase 2

Covers features supported in Flex LSP Phase 2, like SRLG protection and ECMP.

Flex LSP SRLG and Exclude Option for Explicit Path

Explains how to configure SRLG and exclude options for Flex LSP explicit paths.

Flex LSP Non-Revertive 1:1 Path Protection

Guides on configuring non-revertive path protection for Flex LSP.

Flex LSP Sticky

Guides on configuring the sticky option for Flex LSP path protection.

Flex LSP Hop Count and Cost-Max Limit

Explains configuring hop count and accumulated path cost limits for Flex LSPs.

Flex LSP ECMP min-fill, max-fill, random

Details configuring ECMP tie-breakers like min-fill, max-fill, and random for Flex LSPs.

Restore Path Option

Explains how to configure and verify the restore path option for Flex LSP tunnels.